Hello all AM,ers. I completed the pair of 4D32 rf deck today, minus the negative cycle loading setup (waiting for the 14KV 1 amp diodes), and did some haywire JS type testing. First was the grid circuit, I needed to unwind a few turns off the grid coil to get it to resonate in the 40 meter band. I then put screen and plate voltage on, using a heathkit variable high voltage supply for the screens, the variac power supply for the big rig modulator did the plate supply.
With 25-30 ma of grid drive, 300 volts on the screens, and 600 to 1000 volts on the plates, I get 200 to 250 watts out. Seems to tune very nicely indeed. I tried various plate voltages and currents, but need to calculate just what current I could run at 1000 volts. At 1000 volts and 300 ma, I got the 250 watts out. It would seem that is 25 watts dissipation per tube. The rating on a 4D32 is 50 watts of plate dissipation. I also need to look at the spectrum analyzer to check harmonics and so on. So far, it came out very nice looking, no extra holes, or holes off/in the wrong place. The paint came out nice, gray chassis, black front panel. I found some epoxy paint for the front panel, its supposed to be for appliance painting, needs no primer, and is supposed to be very tough (home depot). It does not seem to come in gray though... I guess the RF control deck is next, LOADS of variacs, meters, relays, switches, etc. It will have a variac bias supply, adjustable grid leak resistance, a variac screen supply with an adjustable series resistance, a choke for screen modulation, a screen overload relay setup, meters to measure grid voltage, grid current, screen voltage, each screen current and both combined, plate current for the 4D32's, push to talk power supply and relays, negative cycle loading variac power supply with voltage and current, and other things. (a lot of work) The modulator will also be complex.... Brett N2DTS
